1. Field of the Invention
The present invention relates an electron emission device having an electron emitter for emitting electric-field electron emission and a production method of the same and in particular, to an electron emission device having a four-layered configuration of electrodes via an insulation layer and its production method.
2. Description of the Prior Art
These years, development and study on the display apparatus have been directed to reduction in the thickness of the display apparatus. A special attention is paid on electric field emission type display apparatus (hereinafter, referred to as an FED) using so-called electron emission devices.
In this FED, each pixel is constituted by an electron emission device in combination with an anode electrode and a fluorescent body which are opposed to the electron emission device. A plurality of such pixels are formed in a matrix to constitute a display apparatus. In this FED, electrons emitted from the electron emission device are accelerated by the electric field between the electron emission device and the anode electrode to attack the fluorescent body. Thus, the fluorescent body is excited to emit light, so as to display an image.
Generally, this electron emission device may be of a spint type or a planar type. The spint type of electron emission device includes an emitter electrode of an approximately conical shape, to which a predetermined electric field is applied so as to emit electrons. Moreover, when producing this spint type of electron emission device, a hole having a diameter of about 1 micrometer is formed and inside this hole, the emitter electrode is formed by way of deposition or the like.
However, in such a spint type of electron emission device, it is difficult to form the aforementioned conical emitter electrode with a desired configuration, disabling to obtain a stable electron emission characteristic. In particular, when producing a large-screen FED, it is necessary to uniformly form the emitter electrodes over a large substrate. In other words, unless the emitter electrodes are formed uniformly, the field electron emission characteristic varies depending on a position on the screen, disabling display of a preferable image.
On the other hand, the planar type electron emission device includes an emitter electrode formed in a flat sheet shape sandwiched via an insulation layer by a pair of gate electrodes, so that an electric field generated between the pair of gate electrodes and the emitter electrode causes the emitter electrode to emit electrons.
In this planar type electron emission device, the emitter electrode for emitting electrons can be formed approximately in a flat sheet shape. Accordingly, this type of electron emission device can be produced easier than the aforementioned spint type electron emission device.
In the planar type electron emission device having the aforementioned configuration, electrons emitted from the emitter electrode are accelerated to attack the fluorescent body in the same way as in the spint type electron emission device. Thus, in the FED using this planar type electron emission device, the fluorescent body is excited to emit light, so as to display an image.
The aforementioned planar type electron emission device is disclosed in U.S. Pat. No. 5,308,439, U.S. Pat. No. 5,604,399, U.S. Pat. No. 5,192,240, Japanese Patent Publication (Unexamined) 2-133397, and Japanese Patent Publication (Unexamined) 7-254354. In the electron emission devices disclosed in these documents, it is difficult to deflect to a desired direction the electrons emitted from the emitter electrode, disabling use of the device in a FED.
In order to solve this problem, as a planar type electron emission device, U.S. Pat. No. 5,124,347 discloses a four-layered electron emission device. In this four-layered electron emission device, a through hole is formed through the pair of electrodes sandwiching the emitter electrode via an insulation layer and an auxiliary electrode is arranged at the bottom of the hole.
In the four-layered electron emission device having the aforementioned configuration, the auxiliary electrode generates an electric field which deflects the electrons emitted from the emitter electrode, to the direction of the anode electrode. Thus, the four-layered electron emission device can effectively make the electrons emitted from the emitter electrode, to attack the fluorescent body on the anode electrode, enabling a display of a comparatively preferable image.
In the aforementioned four-layered electron emission device, the electrons are deflected by the electric field generated by the auxiliary electrode, which may also affect the emitter electrode. That is, in this electron emission device, the electric field generated from the auxiliary electrode affects the vicinity of the tip end of the emitter electrode.
Moreover, the emitter electrode is subjected to an electric field for emitting electrons from the pair of gate electrodes. However, in the conventional four-layered electron emission device, as has been described above, the electric field generated from the auxiliary electrode is applied to the emitter electrode and accordingly, the electric field applied from the pair of gate electrodes to the emitter electrode becomes relatively small.
For this, in the four-layered electron emission device, there is a problem that the electron quantity emitted from the emitter electrode is reduced. In order to compensate this reduction in the electron emission quantity, it is necessary to increase the drive voltage applied to the pair of gate electrodes. In this case, in the electron emission device, it is necessary to increase the voltage resistance of the drive circuit, which significantly increases the production cost.